1. Field of the Invention
This invention relates to digital signal recording and reproducing devices. Specifically, this invention is an apparatus for minimizing the signal distortion, caused by the difference in pick-up and disc characteristic of a high speed optical disc reproducing device.
2. Description of the Related Art
In digital signal recording and reproducing devices, especially optical disc reproducing devices which read data of optical disc at a high speed, such as CD-ROM, DVDP (Digital Versatile Disc Player), DVD-ROM, etc., a signal (input signal) read from an optical disc by a pick-up mechanism has various levels in accordance with its frequency area. This is because the picked-up signal has high frequency components whose amplitudes are lower than that of other frequencies. In addition, the level of the picked-up signal varies with the kind of pick-up (depending on its speed, for example), and kind of disc (CD or DVD).
Therefore, it is preferable to compensate for the attenuation of input signal, and get rid of the group delay deviation. However, a conventional boost circuit allows the gain to be amplified, simultaneously causing the group delay to be altered. As a result, the output signal is distorted. The conventional boost circuit can not be used in optical disc reproducing device which reads data from an optical disc at a high speed, such as CD-ROM, DVDP (Digital Versatile Disc Player), DVD-ROM, etc.
A device which is applicable to high speed optical disc players and CD-ROM, DVD, etc., is required to solve the above-mentioned problem.